Gear Ration?

**Bode71** · 06-03-2012, 07:05 AM

I'm rebuilding the posi traction rearend on my 72 GS 455. The car has around 655 hp and I'm running 275/50R17 on the back and an auto transmission w/o overdrive (the tranny may change to a 4 speed before it's all done though). I'm building the car as an all around car (show/driver) but I want to be able to roast the tires when the conditions require.

And who knows I may have to take some kid to school at a stop light or two.

Any advice would be fantastic!

Thanks,

**Bob** · 06-03-2012, 08:09 AM

With 655 HP, you should be able to roast 'em pretty much any time you want as long as you don't put crazy big tires on the back

**rook1957** · 06-03-2012, 11:05 AM

I have a 1970 El Camino that has a weak 350 in it. It had a 2:72 gear ratio and a 350 th trans. in it when I got it. I first installed a 700r4 to get the lower first gear and the overdrive. At 65 mph the engine ran 1800 rpm. I then installed a 3:73 rear gear and it raised the rpm to 2200 at 65 mph. It gets around town real nice now but suffered about 3 mpg on the highway. It has 255-55 tires on the back.
With my 1972 350 CID Buick it seams to have more touque at a lower rpm than the chevy moter, with the torque you should be getting from the 455 I think that 3:73 would be better than a 4:11 for you unless you never drive it on the highway.
Either way I dont think you will have any problems smoking the tires!
Phil.

**USMC4LIFE** · 06-03-2012, 06:51 PM

THIS IS A BUICK FORUM!!! If you really want to fix it, go rent a cherry picker. Hook the picker to the radiator cap, and lift. Once the cap comes off, drive a Buick under the cap. Lower the cap. Tighten, then drive.....

**rook1957** · 06-05-2012, 07:04 AM

Who is Mr. Bowtie, If you are responding to my reply to what I experienced in my El Camino I thought the information would help with a Buick owner finding a gear ratio. Maybe I should have left out the fact that it was not a Buick!

**Dr. Frankenbuick** · 06-05-2012, 03:36 PM

It's OK Rook, we get what you are saying and appreciate your time to respond.

OP, I think you will not like cruising at high rpms with ratios above 3.55 w/o overdrive. I had a similar powered street/strip car. I went to 4.11s from 3.55s, and I only picked up a 10th of a second in the quarter mile. I hated driving around at over 3000 RPMs to maintain 60 mph. 3.31s ore even 3.08s might be even nicer around town and on the highway, and would still let you roast the tires.

**rook1957** · 06-09-2012, 07:47 AM

Thanks Steve, I agree with you, I have never had the touque that a 455 puts out but I understand they like to pull steep gears!

**carmantx** · 06-10-2012, 06:16 AM

Dale, We run 3:42 in the race car and the red gsx. Good all around gear, and car went 10.71 with that gear, street tires and mufflers with similar HP numbers. We have always used the 8.5" diff. I went to a 3.08 gear in my 72 convertible for more everyday driving and highway driving. The red car has seen plenty of highway miles with these gears. Went to a 4:10 gear in race car once, and went back to 3:42. No gain at track.